1. Field of the Invention
The present invention relates generally to a vehicle such as a bicycle, motorcycle, etc., and, more specifically, to a damper for use in a front fork of the vehicle.
2. Description of the Related Art
FIG. 1 shows a conventional hydraulic shock-absorbing design of bicycle front fork 1. According to this design, the bicycle front fork 1 comprises an upper front fork tube 2, a lower front fork tube 3, and a hydraulic buffer 4 mounted in the upper and lower front fork tubes 2 and 3. The hydraulic buffer 4 comprises an adjustment rod 4a, a piston rod 4b, and damping devices (including oil seals, bearings, rubber rings, spring plates, piston and etc.) 4c forming a fluid loop. The adjustment rod 4a and the piston rod 4b have the respective bottom end extended to the bottom side of the lower front fork tube 3, and the respective top end inserted into the inside of the upper front fork tube 2. The damping devices 4c are fastened to the top end of the piston rod 4b in proper order. During relative motion between the upper front fork tube 2 and the lower front fork tube 3, hydraulic fluid flows in the aforesaid fluid loop, producing a damping effect. Further, the aforesaid adjustment rod 4a is adapted to control the open width of the fluid loop, thereby setting the damping resistance value.
The aforesaid front fork 1 provides a buffering effect; however, the complicated structure of the damping devices 4c greatly increases the manufacturing cost of the front fork 1 and complicates its installation procedure. In order to support the damping devices 4c, the adjustment rod 4a and the piston rod 4b are made having an extended length (see FIG. 1). Increasing the length of the adjustment rod 4a and the piston rod 4b relatively increases the cost.
FIG. 2 shows another design of bicycle front fork 5 according to the prior art. According to this design, the bicycle front fork 5 comprises an upper front fork tube 6, a lower front fork tube 7, a valve bonnet 8 fastened to the bottom end of the upper front fork tube 6, the valve bonnet 8 having a center inlet 8a, two outlets 8b spaced from the inlet 8a at two sides, and two flaps 8c respectively fastened to the bottom wall of the valve bonnet 8 and adapted to close the outlets 8b, a needle valve 9 inserted from the top of the upper front fork tube 6 and approaching the top end of the inlet 8a of the valve bonnet 8, the needle valve 9 having a rear (top) end 9b extended to the outside of the bicycle front fork 5 for receiving an external driving force that is employed to the needle valve 9 to control the distance between the front end 9a of the needle valve 9 and the top end of the inlet 8a of the valve bonnet 8 and to further adjust the damping resistance. The structure of this design of bicycle front fork 5 is relatively simplified; however the needle valve 9 is not durable in use because it directly receives impact pressure from upward flowing of hydraulic fluid passing through the inlet 8a during relative motion between the upper front fork tube 6 and the lower front fork tube 7.
Therefore, it is desirable to provide a front fork having a damper for a vehicle, which can eliminate the drawbacks of the aforesaid prior art designs.